Final Cut Pro 10.6 crash everytime i open it

Adding to Luis' excellent advice, to reset FCP preferences hold down command and option while launching FCP and click Delete Preferences. It will open the default Untitled library. Reopen the library you were working on, set the preferences the way you like, and see if the issue has been resolved.

There have been several problems with 10.6 and Monterey. I am not sure if this is one of them.

Whenever the application crashes, you should delete its preferences - they are corrupted by the crash and will in turn crash it again.

Now, this is not a guarantee that it will work.

If the problem persists, and you can get 10.5.4 (from your Time Machine backup, for example), you may want to get it now, rename it as Final Cut Pro 10.5.4 so you can have both. In case 10.5.4 works, then you have a way out.

Not everyone has severe issues with 10.6, so there is a chance that it will work.

Since you're under deadline, I agree with Luis and recommend rolling back to FCP 10.5.4 from your backups.

Can you find a Mac that's running Catalina? Login with your AppleID originally used to purchase FCP, launch the App Store and click the name at the bottom left. You can download the latest version of FCP that will work on Catalina which is 10.5.4. Zip it up and copy it onto your Monterey Mac.

Or, find a buddy with 10.5.4 and zip up the app and copy it onto your Mac.

Is the Untitled library a working library you’re using?

It’s crashing when you open an empty default Untitled library?

Post an EtreCheck report using the Additional Text button.